Fri Nov  9 13:35:55 UTC 2007  mantoniotti
  * Changed the top comment and added a (:copier nil) option to the
  Changed the top comment and added a (:copier nil) option to the
  ENVIRONMENT defstruct, as COPY-ENVIRONMENT is defined later in the
  file.
  
diff -rN -u old-cl-unification-1/substitutions.lisp new-cl-unification-1/substitutions.lisp
--- old-cl-unification-1/substitutions.lisp	2013-07-25 20:30:50.000000000 +0000
+++ new-cl-unification-1/substitutions.lisp	2013-07-25 20:30:50.000000000 +0000
@@ -1,8 +1,8 @@
-;;; -*- Mode: Lisp -*-
+;;;; -*- Mode: Lisp -*-
 
-;;; substitutions.lisp
-;;; General CL structures unifier.
-;;; Substitution definitions.
+;;;; substitutions.lisp --
+;;;; General CL structures unifier.
+;;;; Substitution definitions.  Mostly a rehash of the usual SICP stuff.
 
 (in-package "CL.EXT.DACF.UNIFICATION") ; DACF = Data And Control Flow.
 
@@ -76,7 +76,8 @@
 ;;;---------------------------------------------------------------------------
 ;;; Environments.
 
-(defstruct (environment (:print-object print-environment))
+(defstruct (environment (:print-object print-environment)
+                        (:copier nil))
   (frames () :type list))
 
 (defun print-environment (env stream)
@@ -137,4 +138,4 @@
     env))
 
 
-;;; end of file -- substitutions.lisp --
+;;;; end of file -- substitutions.lisp --